CAIRO — American- and British-made bombs may have killed or injured nearly 1,000 civilians, including women and children, in Yemen’s four-year conflict, according to a report released Wednesday by human rights groups.

The airstrikes killed 203 people and injured at least 749, the report found. At least 122 children and 56 women were among the dead and wounded.

U.S. and British lawmakers have mounted efforts to stop arms sales and end their countries’ involvement in Yemen’s civil war, which has created what the United Nations describes as the world’s most severe humanitarian crisis.

The United States, in particular, has sold billions of dollars in weaponry to Saudi Arabia and the United Arab Emirates, its key allies in the Middle East. Both nations lead a regional coalition that seeks to oust northern rebels known as Houthis and restore Yemen’s internationally recognized government.

Washington is also assisting the coalition with intelligence, training and other forms of logistical support.

A Pentagon spokeswoman said the United States does not investigate airstrikes by the coalition, but “we have consistently discussed and reinforced procedures to limit civilian casualties.”

“We have repeatedly urged the Saudi-led coalition to address shortcomings in their operations that have led to civilian casualties, and have worked with them to develop procedures and oversight mechanisms to reduce such incidents,” said Cmdr. Rebecca Rebarich.

In their 128-page report, the U.S.-based University Network for Human Rights and a well-known Yemeni rights group, Mwatana, probed 27 coalition airstrikes between April 2015 and April 2018 — all against civilian targets.

In 25 of the assaults, investigators determined that U.S.-made munitions, including banned cluster bombs, were likely to have been used. In five of the strikes, British-made weaponry appears to have been deployed, the report said.

There were 16 airstrikes on civilian gatherings or homes, five on educational and health facilities, five on civilian businesses and one on a government cultural center.

“Our findings reinforce prior evidence demonstrating that the Saudi/UAE-led Coalition is failing to fulfill its obligations under the laws of war and repeatedly using US weapons in apparently disproportionate and indiscriminate attacks that have resulted in widespread civilian casualties and other civilian harm in Yemen,” the report said.

The findings hint at the real civilian toll of the war. From March 2015 to April 2016 alone, more than 18,000 coalition airstrikes pounded Yemen, nearly a third striking civilian targets, according to the Yemen Data Project, an independent monitoring group.

The report strongly suggested that the air assaults could be unlawful under international law and constitute potential war crimes.

“Many of the attacks appeared to take place far from any potential military target,” the report said. “Others caused harm to civilians that vastly outweighed any likely military benefit. In no case did it appear that coalition forces took adequate precautions to minimize harm to civilians, as required by international humanitarian law.”

A spokesman for the Saudi-led coalition did not respond to a request for comment, but the coalition has frequently denied allegations that it is targeting civilians.

In 2017, the coalition said it would launch a training program to reduce what it described as accidental targeting of civilians. But those pledges fell short. In the year since the announcement, civilian deaths were 7 percent higher than the previous year, according to United Nations data.

Saudi Arabia and its regional allies entered the war in March 2015, weeks after the Houthis drove out Yemen’s president from the capital, Sanaa. Saudi Arabia, the region’s leading Sunni power, is seeking to prevent Shiite Iran’s theocracy from gaining influence in the Middle East through its alliance with the Houthis, who belong to the Zaidi branch of Shiite Islam.

The conflict has driven millions of Yemenis to the edge of famine and displaced more than 3 million. The United Nations says a child dies every 10 minutes in the country, which is the Middle East’s poorest. With the health system on the verge of collapse, thousands have died of easily preventable illnesses.

In December, the U.S. Senate voted to end American support for the coalition in Yemen, driven partly by the rising civilian death toll — which some estimates put in the tens of thousands — as well as the specter of a looming famine. The measure was also seen as a rebuke of the Saudi government for its conduct of the war and its role in the killing of Washington Post contributing columnist ­Jamal Khashoggi in October.

Last month, the House also passed a resolution to withdraw U.S. support for the war, and the Senate is scheduled to vote again on the measure in the upcoming weeks. Despite the growing opposition, President Trump has indicated that he would veto the legislation.